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Identification of two inactive forms of the central sulfur cycle protein SoxYZ of Paracoccus pantotrophus
Author(s) -
Quentmeier Armin,
Li Lin,
Friedrich Cornelius G.
Publication year - 2008
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2008.09.043
Subject(s) - tcep , chemistry , heterotetramer , iodoacetamide , sulfide , cysteine , enzyme , tris , protein subunit , dithiothreitol , biochemistry , active site , phosphine , organic chemistry , catalysis , gene
The central protein of the sulfur‐oxidizing enzyme system of Paracoccus pantotrophus , SoxYZ, reacts with three different Sox proteins. Its active site Cys110 Y is on the carboxy‐terminus of the SoxY subunit. SoxYZ “as isolated” consisted mainly of the catalytically inactive SoxY‐Y(Z) 2 heterotetramer linked by a Cys110 Y ‐Cys110 Y interprotein disulfide. Sulfide activated SoxYZ “as isolated” 456‐fold, reduced the disulfide, and yielded an active SoxYZ heterodimer. The reductant tris(2‐carboxyethyl)phosphine (TCEP) inactivated SoxYZ. This form was not re‐activated by sulfide, which identified it as a different inactive form. In analytical gel filtration, the elution of “TCEP‐treated” SoxYZ was retarded compared to active SoxYZ, indicating a conformational change. The possible enzymes involved in the re‐activation of each inactive form of SoxYZ are discussed.